The present invention relates generally to charge pump power supplies, and more particularly, to a high efficiency step-down/step-up and step-up/step-down charge pump.
A voltage converter can be used to convert a lower voltage to a higher voltage (step-up operation) or to convert a higher voltage to a lower voltage (step-down operation). In some cases, a switched capacitor DC/DC converter employing a fractional conversion technique may be used. This technique reconfigures power switches based on input voltage (Vin) and output voltage (Vout) to achieve higher power efficiency than linear regulation does. Typical switch configurations for step-up operation include 1:1, 2:3, 1:2 and 1:3, and typical switch configurations for step-down operation include 1:1, 3:2, 2:1 and 3:1.
Some previously developed charge pumps are capable of providing only one direction of voltage conversion-either step-up or step-down. Other previously developed charge pumps are capable of both step-up and step-down operation. However, such other previous designs are efficient only one direction of voltage conversion. That is, a previously developed charge pump which can efficiently convert a lower voltage to a higher voltage cannot efficiently convert a higher voltage to a lower voltage. Likewise, a previously developed charge pump which can efficiently converts a higher voltage to a lower voltage cannot efficiently convert a lower voltage to a higher voltage.
Embodiments of the present invention include a charge pump capable of providing both step-down and step-up operation in an efficient manner.
In one aspect, a charge pump power supply circuit generates a regulated output voltage higher or lower than an input voltage. Such power supply circuit can be integrated on a single piece of semiconductor substrate material. In another aspect, other circuitry may be integrated on a single piece of semiconductor substrate material along with such a power supply circuit.
According to one embodiment of the present invention, a charge pumping system capable of a forward operation mode and a reverse operation mode is provided. In forward operation mode the charge pumping system can step-up an input voltage at a ratio of 1/2:1 and can step-down the input voltage at a ratio of at least one of 1:1, 3:2, 2:1 and 3:1. In reverse operation mode the charge pumping system can step-down the input voltage at a ratio of 1:xc2xd and 1:1 and can step-up the input voltage at a ratio of at least one of 2:3, 1:2 and 1:3.
According to another embodiment of the present invention, a charge pumping system capable of a forward operation mode and a reverse operation mode is provided. The system includes a first node operable to be connected as an input node in the forward operation mode and as an output node in the reverse operation mode. A second node operable to be connected as an input node in the reverse operation mode and as an input node in the forward operation mode. In forward operation mode the charge pumping system can step-up an input voltage at a ratio of xc2xd:1 and can step-down the input voltage at a ratio of at least one of 1:1, 3:2, 2:1 and 3:1. In reverse operation mode the charge pumping system can step-down the input voltage at a ratio of 1:xc2xd and 1:1 and can step-up the input voltage at a ratio of at least one of 2:3, 1:2 and 1:3. A switching component, connected to the first node and the second node, is operable to be configured to set the ratio for step-up or step-down for the forward and reverse operation modes. The switching component may comprise at least one fractional switch having a plurality of segments.
Regulated step-up/step-down charge pump including 1:1, 2:3, 1:2 and 1:3 modes converts a lower input voltage to a higher output voltage using 2:3, 1:2 and 1:3 modes and converts a higher voltage to a lower voltage using 1:1 mode. Regulated step-down charge pump including 1:1, 3:2, 2:1 and 3:1 modes can only provide a lower output voltage from a higher input. Increasing from 4 modes to 5 modes by adding xc2xd:1 to step-down charge pump and by adding 1:xc2xd to step-up/step-down charge pump will have two advantages. One is increasing battery life and the other is improving power efficiency.
Other aspects and advantages of the present invention will become apparent from the following descriptions and accompanying drawings.
For a more complete understanding of the present invention and for further features and advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:
FIG. 1A is a schematic diagram of a charge pumping system, according to an embodiment of the present invention.
FIG. 1B is a schematic diagram of an exemplary implementation for the charge pumping system depicted in FIG. 1A.
FIGS. 2A-2E are schematic diagrams illustrating switch settings of the exemplary implementation for a number of modes for the charge pumping system.
FIG. 3 is a schematic diagram of an exemplary implementation for a fractional switch, according to an embodiment of the present invention.
FIG. 4 is a schematic diagram of a circuit for assigning reverse/forward functions for nodes of a system, according to an embodiment of the present invention.
FIG. 5 is a schematic diagram of an approach for implementing fractional switching, according to an embodiment of the present invention.
FIG. 6 is a schematic diagram of another approach for implementing fractional switching, according to an embodiment of the present invention.
FIG. 7 is a schematic diagram of yet another approach for implementing fractional switching, according to an embodiment of the present invention.